1. Field of the Invention
The present invention relates to a MEMS scanner package. More particularly, the present invention relates to a MEMS scanner package used for a projector for projecting an image and a scanning projector including the same.
2. Description of the Related Art
Recently, with the increase in the consumption of high-quality and large-capacity multimedia content, the demand for large-scale display screens having high image quality has risen.
A projector is one such display device, which projects an image, and may be used for a projector for projecting an image to be presented in a conference room, a commercial movie theater projector, a home theater projector, etc.
A scanning projector generates an image on a screen by scanning light using a scanner, and has the advantage of easily realizing a large-scale screen in comparison with other display devices.
Meanwhile, in the scanning projector, light is projected onto a screen after passing through various optical components, such as an optical system, which includes a light source, a filter, a mirror, and a lens, a scanner, a distortion correction lens, etc.
FIG. 1 is a conceptual view illustrating a scanning projector.
Referring to FIG. 1, a scanner 140 in a scanning projector sequentially and repeatedly performs first directional scanning and second directional scanning, and outputs light onto an external projection area.
The scanner 140 may be implemented as a scanner package that includes a magnetic body for supplying electromagnetic force to the scanner 140.
FIG. 1 illustrates a projection image based on visible light (RGB) in the state of being output from the scanning projector onto the projection area of a screen 102.
Referring to FIG. 1, the scanning projector may include a plurality of light sources 110r, 110g and 110b, a light reflection unit 123, light wavelength splitting units 124 and 125, and a scanner 140.
Meanwhile, when light from the light sources 110r, 110g and 110b is projected to an external object, it is important to collimate the light. To this end, laser diodes may be used.
Meanwhile, the light sources 110r, 110g and 110b may include a blue laser diode 110b for outputting blue light, a green laser diode 110g for outputting green light, and a red laser diode 110r for outputting red light.
The arrangement and positions of the light sources and other optical components may be variously changed depending on the design specifications.
For example, the light output from the light source 110b may be reflected by the light reflection unit 123, may be transmitted by the light wavelength splitting unit 124, and may be incident upon the scanner 140.
Also, the light output from the light source 110g may be reflected by the light reflection unit 124, may be transmitted by the light wavelength splitting unit 125, and may be incident upon the scanner 140.
Also, the light output from the light source 110r may be reflected by the light wavelength splitting unit 125 and may be incident upon the scanner 140.
The light wavelength splitting units 124 and 125 may reflect or transmit light based on the wavelength of the light. For example, the light wavelength splitting units 124 and 125 may be embodied as dichroic mirrors.
When the wavelength of any one light source is shorter than the wavelength of another light source, the light wavelength splitting units 124 and 125 may transmit the light having a shorter wavelength, and may reflect the light having a longer wavelength.
Meanwhile, the optical system 120 illustrated in FIG. may include a light reflection unit 123 and light wavelength splitting units 124 and 125.
Meanwhile, the scanner 140 may receive the output light from the light sources 110r, 110g and 110b, and may sequentially and repeatedly perform first directional scanning and second directional scanning to the outside.
The scanner 140 may receive the synthesized light from the optical system 120, and may project the synthesized light in a horizontal direction and a vertical direction. For example, the scanner 140 may project the synthesized light in the horizontal direction with respect to a first line (horizontal scanning), and may move vertically to a second line below the first line (vertical scanning). Subsequently, the scanner 140 may project the synthesized light in the horizontal direction with respect to the second line (horizontal scanning). In this manner, the scanner 140 is capable of projecting an image to be displayed onto the entirety of the screen 102.
As shown in the drawing, the scanner 140 may perform horizontal scanning from left to right, vertical scanning from top to bottom, horizontal scanning from right to left, and vertical scanning from top to bottom of the area that can be scanned. This scanning operation may be repeatedly performed over the entirety of the projection area.
Meanwhile, the scanner 140 may be a micro-electro-mechanical system (MEMS) scanner. The scanner 140 may be driven horizontally or vertically, depending on the resolution or system conditions, by a magnetic field generated by a magnet and a coil in a magnetic manner, and may reflect light.
If any optical component in the scanning projector cannot accurately reflect or transmit light according to the design specifications, the quality of an image may be deteriorated, or an image may be displayed inaccurately.
Further, because the scanning projector generates an image through rotation of the scanner, it is important to rotate the scanner precisely so that the scanning projector generates an accurate image.
Furthermore, the scanning projector has a problem in that, when driven for a long time period, components may be damaged, or the performance, such as a reflectivity, may be deteriorated due to excessive rotational operation of the scanner.
FIGS. 2A, 2B and 3 are views for explaining a reflectivity deterioration phenomenon of the scanner during operation thereof.
Referring to FIGS. 2A and 2B, the scanning projector using a MEMS scanner has a problem in that foreign substances 201, such as dust, adhere more and more to a mirror surface 211 of the MEMS scanner while the MEMS scanner is driven.
This problem causes deterioration in the reflectivity of the mirror surface 211 of the MEMS scanner.
Referring to FIGS. 2A and 2B, an edge portion 211b of the mirror surface 211 of the MEMS scanner is covered with more foreign substances, such as dust, than a central portion 211a of the mirror surface 211.
This is because, like the adhesion of dust to the blades of a fan, the linear velocity at the edge portion 211b is larger than that at the central portion 211a when the MEMS scanner rotates, and consequently the extent of exposure of the edge portion 211b to dust in the air is higher.
While the central portion 211a of the mirror surface 211 of the MEMS scanner maintains reflectivity of 80 percent or more, the edge portion 211b, to which foreign substances, such as dust, readily adhere, has considerably deteriorated reflectivity.
Accordingly, the brightness of the scanning projector may also be reduced to half its original brightness or less.
FIG. 3 shows brightness for respective colors and the brightness change rate before and after the long-term operation of the scanning projector.
Therefore, in order to solve the above problems, a MEMS scanner package structure capable of minimizing exposure of the scanner to external dust has been devised.
Further, research into a method of accurately performing the function of respective optical components of the scanning projector and into improving the reliability upon long-term operation has been carried out.